The Sand Springs terrane is a highly deformed, thick, mainly basinal volcanogenic assemblage of rocks at least partly of early Mesozoic age and possibly having affinities with rocks of the Black Rock-Jackson terrane (Silberling, 1991). The presumably oldest Mesozoic rocks are volcanogenic and carbonate turbidites interbedded with mudstone which grade upward into interbedded basinal carbonates and volcanogenic rocks containing Late Triassic faunas (Oldow, 1984a). Elsewhere, interbedded carbonate, volcanic, and volcanogenic rocks are assigned an Early to Middle Jurassic age and represent relatively shallow-marine to subaerial deposition (Oldow, 1984a). Although structural relations in the Sand Springs terrane are locally complicated by later Cenozoic deformation, the rocks appear to have been involved in major northwest-southeast shortening between the Early Jurassic and Late Cretaceous (80 Ma) (Oldow, 1984a). The rocks of the Sand Springs terrane crop out in southern Washoe, Pershing, Churchill, Mineral, and northern Nye Counties.